In recent years, with the rapid development of technologies, mobile products having a biological identification function have gradually entered people's life and work. Great importance is attached to a fingerprint technology by right of its unique identity characteristic.
Push-type and sliding-type fingerprint identification technologies on the basis of silicone-based process have been integrated into mobile products. In the future, people will likely focus their attention on a fingerprint identification technology in a display area. When a fingerprint device based on an image sensor is scanning fingerprints, the light that a light source irradiated onto fingers will result in different reflections due to the difference between ridges and valleys of a fingerprint, thereby leading to variation of intensity of light arriving at a photosensitive device and generating dissimilar photocurrent differences. Under the control of a control device, the current differences of the sensing devices are read out in sequences in order to achieve the detection of ridges and valleys of the fingerprint.
Since the sensing device itself has leakage current, it greatly affects the detection of ridges and valleys of the fingerprint and the extraction of feature information. Under the influence of the difference of processes and the consistency of devices, different sensors have extremely different leakage currents, which can hardly be calculated in a uniform way.